Gil Kalai’s blog

Tag Archives: Sex

“251 Mercer street” I said, “it is in the village,” “I know that” said the driver “are you going to NYU?” “Yes” I said. I was going to give a lecture at Ricky and Eli’s Tuesday evening’s Geometry Seminar and came earlier to have a chance to chat with the guys. “Let me tell you something” the driver said, “I did not finish elementary school, I left in the 6th grade and started working, and everyday I come home and have sex. My friends who finished elementary school have sex 2-3 times a week, tops. And , you know,” continued the driver “those who went on to finish high school, they have sex maybe once a week, no more.” “I see,” I said. Continue reading →

1. What are Chip firing games?

Many women will find it admirable
if you tell her she makes your CHIPS FIRABLE.

Chip firing games are (solitary) games played on graphs: each node of a directed graph contains a pile of chips. A move consists of selecting a node with at least as many chips as its outdegree, and sending one chip along each outgoing edge to its neighbors. The remarkable property of these games is that depending on the sizes of the piles, either the game continues forever or it reaches a position where it cannot be played further. In the latter case the final position, the number of moves, and even the number of times each node fired do not depend on the specific moves made along the game.

Sheep firing game (You may play the game by clicking on the picture; disclaimer: we object to cruel treatment of animals)

In the rest of this post you can read about shellability, weak and strong (Bruhat) partial orders on the set of permutations, chessboard complexes, and more. Continue reading →

The girls today in society
go for great mathematics, see.
So to win their hearts you must quote with ease
Pythagoras and Archimedes.
One must know Newton and Gauss and, hey,
what’s his name, eh? Poincaré!
Unless you know Grothendieck and DesCartes
no sweet lady will give you her heart.
But to really make them fall
and to make your love-life surrealist,
quote the greatest of them all:
a 60-year old comb’naturrealist.

Brush up your Björner,
start quoting him now!
Brush up your Björner,
and the ladies you will wow.

Many women will find it admirableif you tell her she makes your CHIPS FIRABLE.
If your lady-friend still isn’t yielding
say you’ve got this big place: a TITS BUILDING.
If there still is some source of estrangement
make some cozier SUBSPACE ARRANGEMENT.
Brush up your Björner,
and they’ll all be charmed!

I was asked by the Notices of the AMS to review the book “More Sex is Safe Sex: The Unconventional Wisdom of Econmics” by Steven E. Landsburg. My review entitled “Economics and Common Sense”, will appeared in the June/July issue of the Notices and you can find it here. (And in the August issue of the AMS Notices, there is will be a book review by Olle Häggström on John Allen Paulos’ new book: “Irreligion”.)

In his book, Steven E. Landsburg uses the “weapons of evidence and logic, especially the logic of economics” to draw surprising insights which run against common sense. “If common sense tells you otherwise,” says Landsburg, “remember that common sense also tells you that the Earth is flat”.

I will include a few little sectionettes from the review here in this post. Some of the issues raised in this book are related to many discussions and debates we had over the years at the Center for the Study of Rationality of the Hebrew University of Jerusalem. Questions regarding “efficiency,” “subsedies,” “monopolies,” “labor union,” “differential salaries,” “law and economics,” “rationality and the judicial system,” and various other related topics were amply discussed at the Center, and some of these topics and discussions are related to issues raised in Landsburg’s book.

The Armchair Economist

Sometime after writing my review, I saw in the Yale book store, along with several copies of Landsburg’s new book, a copy of his older book from the early 90s, “The Armchair Economist”. I bought it and read some of the chapters. So before quoting excerpts from my book review on the new book let me first talk a little bit about the older book. Several chapters are devoted to describing some classic teachings of economics, such as general equilibrium theory, and they are very good. I liked Landsburg’s explanation of the notion of “efficiency” – it is the best popular explanation of “efficiency” I read or listened to.

The Peltzman Effect

Armchair Economist starts with an interesting finding from the 1970s by Sam Peltzman, a U. of Chicago economist, asserting that safety seat belts have led to an increase in the number of car accidents, and that the net effect on death from car-accidents, which is reduced by the direct effect of seat belts and other safety measures, but which at the same time is increased by the indirect effect of drivers taking more risks because of these safety measures, is close to zero. Peltzman’s study also asserts that seat belts have raised pedestrian death toll caused by accidents.